正則表達式的解釋

我是相當新的正則表達式，我在perl腳本stubled在一個正則表達式最近，我無法弄清楚：正則表達式的解釋

$groups= qr/\(([^()]+|(??{$groups}))*\)/;

任何幫助，將不勝感激！

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2011-12-10 Kalamari

那麼，如果你展開：

$groups= qr/ 
    \(    # match an open paren (
    (    # followed by 
     [^()]+   # one or more non-paren character 
    |    # OR 
     (??{$groups}) # the regex itself 
    )*    # repeated zero or more times 
    \)     # followed by a close paren) 
/x;

你得到一個優雅的遞歸方法找到平衡括號:)

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2011-12-10 01:53:12 FailedDev

啊！這就說得通了。什麼是/ x最終我從來沒有見過。 – Kalamari

@Kalamari這是可用空間的標誌。它允許我以更易讀的方式編寫正則表達式，並在其中添加解釋。 – FailedDev

@Kalamari，'''/ x'''可以讓你把它分開，並且包含註釋。它基本上意味着「忽略白色空間......和評論」。 – FakeRainBrigand

的YAPE::Regex::Explain模塊可以告訴你什麼是正則表達式是這樣做的：

% perl5.14.2 -MYAPE::Regex::Explain -E 'say YAPE::Regex::Explain->new(shift)->explain' '\(([^()]+|(??{$groups}))*\)' 
The regular expression: 

(?-imsx:\(([^()]+|(??{$groups}))*\)) 

matches as follows: 

NODE      EXPLANATION 
---------------------------------------------------------------------- 
(?-imsx:     group, but do not capture (case-sensitive) 
         (with^and $ matching normally) (with . not 
         matching \n) (matching whitespace and # 
         normally): 
---------------------------------------------------------------------- 
    \(      '(' 
---------------------------------------------------------------------- 
    (      group and capture to \1 (0 or more times 
          (matching the most amount possible)): 
---------------------------------------------------------------------- 
    [^()]+     any character except: '(', ')' (1 or 
          more times (matching the most amount 
          possible)) 
---------------------------------------------------------------------- 
    |      OR 
---------------------------------------------------------------------- 
    (??{$groups})   run this block of Perl code (that isn't 
          interpolated until RIGHT NOW) 
---------------------------------------------------------------------- 
)*      end of \1 (NOTE: because you are using a 
          quantifier on this capture, only the LAST 
          repetition of the captured pattern will be 
          stored in \1) 
---------------------------------------------------------------------- 
    \)      ')' 
---------------------------------------------------------------------- 
)      end of grouping 
----------------------------------------------------------------------

您可以將這一行代碼變成您個人資料中的別名：

alias re="perl -MYAPE::Regex::Explain -E 'say YAPE::Regex::Explain->new(shift)->explain'"

之後，你不必記住所有：

re '\(([^()]+|(??{$groups}))*\)'

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2011-12-10 10:33:31

正則表達式的解釋

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